1. Field of the Invention
The present invention relates to a variable magnification optical system which guides light from a photographing target (on the object side) to an image sensor, and an image-taking apparatus provided with such a variable magnification optical system. More specifically, the present invention relates to a variable magnification optical system provided with vibration-proof function and an image-taking apparatus provided with such a variable magnification optical system.
2. Description of the Related Arts
Conventionally, various interchangeable lenses for use in single-lens reflex cameras or the like have been developed. Moreover, various interchangeable lenses having vibration-proof function (so-called camera shake correction function) have been developed. One example of the interchangeable lenses having vibration-proof function is disclosed in, for example, patent documents 1 and 2.
Variable magnification optical system having the interchangeable lenses disclosed in these patent documents are arranged with optical power arrangement: “negative, positive, negative, and positive” from the object side to the image side. Such power arrangement is suitable for achieving a wider angle and a higher magnification, and also easily ensures back focus. Therefore, these variable magnification optical systems are preferable for use in single-lens reflex cameras and the like.                [Patent Document] JP-A-H7-152002        [Patent Document] JP-A-H11-174329        
However, the variable magnification optical systems disclosed in patent documents 1 and 2 are not suitable for use in small-size digital cameras (so-called compact digital cameras), due to its insufficient aberration performance in compact digital cameras of a six-million-pixel class which have been recently distributed.
Usually, in zooming performed in a variable magnification optical system having “negative, positive, negative, and positive” optical powers for use in single-lens reflex, a first lens group moves by utilizing a cam ring or the like. However, it is preferable that, for compact cameras which often use an actuator or the like in zooming, the first lens-element be not moved.